The present invention concerns a method of manufacturing a pressurized two-compartment package comprising a container and a bag inside it and having an opening sealed off by a cap with a spray nozzle. The bag collapses when pressure is established between it and the container. Adhesive is applied, prior to insertion of the bag into the container and to pressurization, to the surfaces of essentially cylindrical edges of the container and of the bag that are aligned with the edge of the opening and face each other when the package is used. Once the bag has been inserted into the container, the edge of the bag is spread and forced against the inner surface of the edge of the container by a tool introduced therein. The edges of the container and of the bag are accordingly fastened together tight, and even provided with a bead that can taper toward the opening, by the adhesive. The cap with its nozzle is now placed over the beaded edge. The present invention also concerns a device for carrying out the method.
Such pressurized two-compartment packages and their manufacture are known, from German Patent 3 802 314 for example, which mentions a tool associated with the edge adjacent to the opening but does not specify its design.
The peculiarity of the manufacturing process in question is that the edge of the bag is fastened pressure-tight to the edge of the container, subsequent to which the bag and the container are both deformed until a cap with a nozzle, a spray nozzle for instance, can be fastened pressure-tight to the deformed opening. The bag has always been expanded, to allow the edges to be brought together, by means of plastic tools composed of several parts or segments that together create a tapering central bore. A conical arbor is inserted into the bore, spreading the segments one by one and expanding the tool as a whole. The expansion leaves gaps between the individual segments, allowing the creation of marks in the edge of the bag being expanded. The package can leak. If the outside of the bag has adhesive applied to it in the vicinity of this edge, the surface it is being applied to will be unround, and the adhesive-application heads will be jolted and cannot apply a smooth layer along the circumference. A uniform application of adhesive or uniformly thick layer along the circumference, however, is absolutely essential for the intended tight joint between the edges. Another drawback to plastic tools is the severe thermal stress occasioned by the need to heat the parts of the package during manufacture.
In the past, accordingly, tools of metal, especially steel, have been resorted to, the individual segments secured together by a rubber ring. Such a tool is designed such that the gaps that occur as it expands are occupied by conical sections. The drawback is that the tool is round only at one point along its length, and the diameter cannot be adjusted or corrected.
Furthermore, the gaps are particularly apparent just while the adhesive is being applied, when the tool is only partly open and accordingly unround, which again jolts the applicators. The adhesive will not be applied evenly, producing more marks as it spreads. Such a tool is also very expensive.
Objects of the present invention are accordingly a simple method of the aforesaid genus and a device for carrying out the method wherein the edges of the bag can be spread absolutely smooth.
The method is attained in accordance with the present invention in that the tool is a resilient piece that can be compressed more or less perpendicular to the plane of the opening, its outside diameter slightly shorter while the bag is being inserted into the container than the inside diameter of the edge of the bag and subsequently increasing constantly and uniformly radially with a continuous circumference against the inner surface of the edge of the inner surface of the edge of the bag, gripping it and laying and forcing, as it expands circumferentially, the outer surface of the edge of the bag against the inner surface of the container, subsequent to which the resilient piece is restored to its original shape in the direction opposite that of its expansion, upon which the tightly sealed totality of bag and container is provided with the beading.
The use of a tool in the form of s resilient piece manipulated in accordance with the present method ensures a smooth spread in that axial compression will produce a smooth radial expansion with a circular area on the part of the resilient piece because the axial deformation will result homogeneously throughout the piece in radial expansion, ensuring that the surface will be circular and continuous.
In one preferred embodiment of the method in accordance with the present invention, the adhesive is applied to the outer surface of the edge of the bag, the bag having been drawn over the arbor that accommodates the resilient piece, the resilient piece is compressed to expand it in an initial expansion phase until its circumference is extensive enough to secure the bag firmly, the bag is rotated around an axis perpendicular to the plane of its opening and the adhesive applied to the outer surface of the edge of the bag, the container is advanced into the ready position, and the resilient piece is expanded farther in another expansion phase, completing the spreading of the edge of the bag, which is accordingly forced against the edge of the container.
Since the expansion is entirely uniform in both phases, the adhesive applicators will, upon completion of the first phase, contact the outer surface of the edge of the now rotating edge entirely without jolting, ensuring smooth application of the adhesive. Since the second phase shares this uniformity, the adhesive-coated outer surface of the edge of the bag will be forced against the facing inner surface of the edge of the container just as smoothly, leaving a totally homogeneous layer of adhesive between the two surfaces all the way around and ensuring a tight joint.
In another preferred embodiment, the edge of the opening in at least the container is tapered outward ahead of time. The container and/or bag can also be preferably heated ahead of time. To ensure uniform expansion of the edge of the bag, the resilient piece can be compressed continuously.
The accordingly tight-bonded edges of the package components can now be further processed at the state of the art.
The device for carrying out the method in accordance with the present invention is characterized by an accommodating arbor, a rod, and a cylindrical resilient piece. The two componentsxe2x80x94the container and the bagxe2x80x94of the pressurized two-compartment package can be drawn onto the accommodating arbor with the planes of their openings more or less perpendicular to the main axis of the arbor. The rod extends through s longitudinal cutout in the resilient piece, has a radial stop at the end toward the accommodating arbor, and has associated with it an expansion rod. The expansion rod can be displaced along the rod from away from the stop and toward the resilient piece, forcing the resilient piece against the stop. The resilient piece is accordingly axially shortened and radially expanded.
The expansion rod is preferably provided with a longitudinal bore, which the rod extends through. The rods are accordingly coaxial.
In another preferred embodiment, the resilient piece is accommodated between two supports, especially washers, one at each end, that introduce the force of compression into the resilient piece over an extensive area, preferably over the total annular surface of each cylindrical end.
The rod can furthermore be provided with an initial tubular section that extends through the resilient piece and optionally the supports. The accommodating arbor can also preferably have support-and-guidance components rotationally symmetric to the axis of the rod and secured thereto and/or to the initial tubular section of the expansion rod.
Finally, the rod can be provided with a longitudinal bore, and the components that extend beyond the end of the rod can have openings extending toward the bore, creating a blow-off channel that can be pressurized upon termination of spreading and gluing to allow the resulting two-chamber piece to be removed from the accommodating arbor with compressed air aimed at the floor of the bag.
The resilient piece can be a solid cylinder of elastomer, elastomeric plastic, or resilient composite. It can alternatively be a hollow cylinder containing pneumatic, mechanical, or hydraulic means of smoothly expanding it radially.